2004 YZ250 Top End Rebuild Results

[Moto Man26]

Hey everyone, I just finished rebuilding the motor on my yz250... After assembling the motor, I checked the compression, and I got 170psi cold. That number should be alright? I assume that it will be a bigger number than that when the motor is hot. If so, how much do you estimate... Also for the break-in process, I'll be using a mixture of 20:1, and after the break-in, I'll go to 32:1. Is that ok? Any help will be appreciated!! :cool: :ride: :) :boss: ;)

 

[Lopezracing3]

How long do u plan on breaking it in?

 

[Lopezracing3]

When i build my engine after my races i use 32:1 mixture when i break it in and it has worked for me and i break it in for 5 to 8 hours

 

[Moto Man26]

Ok thanks... But for the compression, do you think it's ok? I assume that it will go up after the break-in process? :cool: :cool:

 

[Lopezracing3]

yea it should go up after u break it in but that compression is real good for a new rebuild

 

[Lopezracing3]

yea it should go up after u break it in but that compression is real good for a new rebuild. most stock bikes have about 140 to 150 psi after it is broken in.

 

[Moto Man26]

Cool, Thanks alot!!! :cool: ;)

 

[Lopezracing3]

remember that it should be that and when it has warmed up it sould be around 170 to 180 psi

 

[kx125412]

Don't use 20:1 it's too much oil and will cause your motor to run hot during break in. Run 32:1 and youll be fine and as for break in no really high rpm's and make sure theres load on the motor. Finding an uphill road or something to burn up and down for an hour is good to start. After that you can ride it like normal. Just make sure the rpm's are varied at all times during break in.

 

[2strokerfun]

20:1 is OK for breakin IF that is what you want to use. Most of us just use the gas/oil mix we are going to run; i.e. 32:1 or whatever you are normally going to use.
do a search for break in procedures. I normally start the bike and warm it up blipping the throttle a bit and not riding it the first time. Once completely warm, stop and let cool completely. Then start and ride low rpms for 10 minutes or so until completely warm. Let cool completely. Then a third time with mid rpms. Let cool again. Recheck head torque and you're good to go.

 

[Moto Man26]

Cool thanks for the tips!:) :cool: :) :ride: